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Diffstat (limited to 'src/pkg/runtime/hashmap.h')
| -rw-r--r-- | src/pkg/runtime/hashmap.h | 147 |
1 files changed, 0 insertions, 147 deletions
diff --git a/src/pkg/runtime/hashmap.h b/src/pkg/runtime/hashmap.h deleted file mode 100644 index 522d1ad01..000000000 --- a/src/pkg/runtime/hashmap.h +++ /dev/null @@ -1,147 +0,0 @@ -// Copyright 2009 The Go Authors. All rights reserved. -// Use of this source code is governed by a BSD-style -// license that can be found in the LICENSE file. - -// This file contains the implementation of Go's map type. -// -// The map is just a hash table. The data is arranged -// into an array of buckets. Each bucket contains up to -// 8 key/value pairs. The low-order bits of the hash are -// used to select a bucket. Each bucket contains a few -// high-order bits of each hash to distinguish the entries -// within a single bucket. -// -// If more than 8 keys hash to a bucket, we chain on -// extra buckets. -// -// When the hashtable grows, we allocate a new array -// of buckets twice as big. Buckets are incrementally -// copied from the old bucket array to the new bucket array. -// -// Map iterators walk through the array of buckets and -// return the keys in walk order (bucket #, then overflow -// chain order, then bucket index). To maintain iteration -// semantics, we never move keys within their bucket (if -// we did, keys might be returned 0 or 2 times). When -// growing the table, iterators remain iterating through the -// old table and must check the new table if the bucket -// they are iterating through has been moved ("evacuated") -// to the new table. - -// Maximum number of key/value pairs a bucket can hold. -#define BUCKETSIZE 8 - -// Maximum average load of a bucket that triggers growth. -#define LOAD 6.5 - -// Picking LOAD: too large and we have lots of overflow -// buckets, too small and we waste a lot of space. I wrote -// a simple program to check some stats for different loads: -// (64-bit, 8 byte keys and values) -// LOAD %overflow bytes/entry hitprobe missprobe -// 4.00 2.13 20.77 3.00 4.00 -// 4.50 4.05 17.30 3.25 4.50 -// 5.00 6.85 14.77 3.50 5.00 -// 5.50 10.55 12.94 3.75 5.50 -// 6.00 15.27 11.67 4.00 6.00 -// 6.50 20.90 10.79 4.25 6.50 -// 7.00 27.14 10.15 4.50 7.00 -// 7.50 34.03 9.73 4.75 7.50 -// 8.00 41.10 9.40 5.00 8.00 -// -// %overflow = percentage of buckets which have an overflow bucket -// bytes/entry = overhead bytes used per key/value pair -// hitprobe = # of entries to check when looking up a present key -// missprobe = # of entries to check when looking up an absent key -// -// Keep in mind this data is for maximally loaded tables, i.e. just -// before the table grows. Typical tables will be somewhat less loaded. - -// Maximum key or value size to keep inline (instead of mallocing per element). -// Must fit in a uint8. -// Fast versions cannot handle big values - the cutoff size for -// fast versions in ../../cmd/gc/walk.c must be at most this value. -#define MAXKEYSIZE 128 -#define MAXVALUESIZE 128 - -typedef struct Bucket Bucket; -struct Bucket -{ - // Note: the format of the Bucket is encoded in ../../cmd/gc/reflect.c and - // ../reflect/type.go. Don't change this structure without also changing that code! - uint8 tophash[BUCKETSIZE]; // top 8 bits of hash of each entry (or special mark below) - Bucket *overflow; // overflow bucket, if any - uint64 data[1]; // BUCKETSIZE keys followed by BUCKETSIZE values -}; -// NOTE: packing all the keys together and then all the values together makes the -// code a bit more complicated than alternating key/value/key/value/... but it allows -// us to eliminate padding which would be needed for, e.g., map[int64]int8. - -// tophash values. We reserve a few possibilities for special marks. -// Each bucket (including its overflow buckets, if any) will have either all or none of its -// entries in the Evacuated* states (except during the evacuate() method, which only happens -// during map writes and thus no one else can observe the map during that time). -enum -{ - Empty = 0, // cell is empty - EvacuatedEmpty = 1, // cell is empty, bucket is evacuated. - EvacuatedX = 2, // key/value is valid. Entry has been evacuated to first half of larger table. - EvacuatedY = 3, // same as above, but evacuated to second half of larger table. - MinTopHash = 4, // minimum tophash for a normal filled cell. -}; -#define evacuated(b) ((b)->tophash[0] > Empty && (b)->tophash[0] < MinTopHash) - -struct Hmap -{ - // Note: the format of the Hmap is encoded in ../../cmd/gc/reflect.c and - // ../reflect/type.go. Don't change this structure without also changing that code! - uintgo count; // # live cells == size of map. Must be first (used by len() builtin) - uint32 flags; - uint32 hash0; // hash seed - uint8 B; // log_2 of # of buckets (can hold up to LOAD * 2^B items) - uint8 keysize; // key size in bytes - uint8 valuesize; // value size in bytes - uint16 bucketsize; // bucket size in bytes - - byte *buckets; // array of 2^B Buckets. may be nil if count==0. - byte *oldbuckets; // previous bucket array of half the size, non-nil only when growing - uintptr nevacuate; // progress counter for evacuation (buckets less than this have been evacuated) -}; - -// possible flags -enum -{ - IndirectKey = 1, // storing pointers to keys - IndirectValue = 2, // storing pointers to values - Iterator = 4, // there may be an iterator using buckets - OldIterator = 8, // there may be an iterator using oldbuckets -}; - -// Macros for dereferencing indirect keys -#define IK(h, p) (((h)->flags & IndirectKey) != 0 ? *(byte**)(p) : (p)) -#define IV(h, p) (((h)->flags & IndirectValue) != 0 ? *(byte**)(p) : (p)) - -// If you modify Hiter, also change cmd/gc/reflect.c to indicate -// the layout of this structure. -struct Hiter -{ - uint8* key; // Must be in first position. Write nil to indicate iteration end (see cmd/gc/range.c). - uint8* value; // Must be in second position (see cmd/gc/range.c). - - MapType *t; - Hmap *h; - byte *buckets; // bucket ptr at hash_iter initialization time - struct Bucket *bptr; // current bucket - - uint8 offset; // intra-bucket offset to start from during iteration (should be big enough to hold BUCKETSIZE-1) - bool done; - - // state of table at time iterator is initialized - uint8 B; - - // iter state - uintptr bucket; - uintptr i; - intptr check_bucket; -}; - |